1. Field of Invention
The present invention relates to a hybrid type vehicle drive control device, a hybrid type vehicle drive control method, and a program therefor.
2. Description of Related Art
In the related art, there is a vehicle drive apparatus, which is mounted on a hybrid type vehicle and which transmits a portion of the torque of an engine, i.e., an engine torque, to a generator (or a generator motor) and the remainder to a drive wheel. This vehicle drive apparatus includes a planetary gear unit composed of a sun gear, a ring gear and a carrier, and generates a drive force by connecting (1) the carrier and the engine, (2) by connecting the ring gear, the drive motor and the drive wheel, and (3) by connecting the sun gear and the generator, thereby to transmit the rotations outputted from the ring gear and the drive motor to the drive wheel.
In the vehicle drive apparatus of this kind, in case the speed of the generator, i.e., the generator speed is low, the power consumption is increased which lowers the power efficiency of the generator and deteriorates the mileage of the hybrid type vehicle accordingly. In case the generator speed is low, therefore, a generator brake acting as a generator fixing mechanism is applied to stop the switching of the generator thereby to stop (or shut down) the generator. When a generator target speed indicating the target value of the generator speed exceeds a predetermined threshold value, the generator brake is released to drive the generator.
When the driver depresses the brake pedal while the hybrid type vehicle is driven with the generator brake being applied, on the other hand, the speed of the ring gear, i.e., the ring gear speed lowers as the vehicle speed lowers. At this time, however, a generator target speed is raised to correspond to the speed of the engine, i.e., the engine target speed indicating the target value of the engine speed and the ring gear speed, thereby to release the generator brake.
In order that the generator speed may not fluctuate according to the release of the generator brake, moreover, a generator torque, i.e., the torque of the generator, having the same magnitude as that of an engine torque to be transmitted to the generator is generated in the opposite direction to the engine torque (as referred to Patent Publication JP-A-9-100853).